a. Field of the Invention
This invention relates to a method and apparatus for performing a desired operation in a selected mandrel of a well having a tubing string and at least one mandrel at an intermediate location in the tubing string. More particularly this invention relates to a running assembly including operating tool means to perform the desired operation and selector stop means to positively locate the operating tool means with respect to the selected mandrel. The apparatus is constructed so that once the selector stop means locates the operating tool means, manipulation of the operating tool means to perform the desired operation disengages the selector stop means. Additionally, this invention relates to a method of utilizing a running assembly to positively locate operating tool means with respect to a selected mandrel when the tubing string has at least one mandrel at an intermediate location in the string, and from that location, manipulating the operating tool means to perform the desired operation in a selected mandrel.
B. The Prior Art
A well is often equipped with at least one mandrel in which an operation will be performed at an intermediate position within the tubing string. Generally a plurality of such mandrels are positioned within the tubing string and an identical operation may be performed in each mandrel. A single type of operating tool means may be utilized. To perform the operation in the proper mandrel the location of the tool must be known.
When wire line equipment is employed, it is possible to determine the location of the operating tool means with respect to any selected mandrel by measuring the length of the line that has been paid out.
Where pumpdown equipment is utilized no satisfactory method of determining the position of the operating tool has been available. Conventionally, two types of systems are used to ascertain the location of a pump down running assembly. Both systems are unable to positively locate the running assembly in intermediate positions in the tubing string.
One system attempts to locate the running assembly by measuring the amount of fluid pumped into the well. Inaccurate locations are calculated with this system because of fluid seepage past the pump down locomotives and because of trapped gases in the column of pumped fluids.
In the second conventional system, a plurality of nipples with a restrictive bore are placed in the tubing string. The running assembly is temporarily impeded when passing through such a nipple. The purpose of impeding movement of the running assembly is to create a registrable increase in fluid pressure. Unfortunately, such nipples also contribute to the hanging up of the running assembly. In addition, they do not provide a good indication of where the running assembly is located because it may also hang up on other obstructions in the tubing. Such an unintended hangup provides a pressure increase similar to the pressure increase which occurs when the running assembly passes through a restrictive bore nipple.
Thus, at depths in excess of several thousand feet, it is presently impossible to accurately locate the pumpdown running assembly in the drill string. As mandrels are often positioned within a couple of hundred feet of each other, the error associated with locating a pump down running assembly means that the operator is unable to ascertain if the running assembly is in the vicinity of a selected mandrel in which he wants to perform a desired operation or if it is in the vicinity of some other mandrel. Performing the operation in the wrong mandrel, at the very least, means that the running assembly has to be removed from the well, redressed, and rerun in an attempt to perform the operation in the selected mandrel, all at a considerable waste of time and expense. Other consequences of performing the operation in the wrong mandrel, such as killing the well, killing the wrong zone, treating the wrong zone, or allowing two zones to communicate with each other, are much more serious.
Some running assemblies include a locator tool means. The locator tool means carries locator keys which are matched with the internal recess of a predetermined locator nipple. Upon movement of the running assembly through the well tubing, the locator keys engage the recess of the predetermined locator nipple to position the running assembly. With the locator keys remaining in position, pins are sheared and/or telescoping sleeves moved to permit operation of the work tool. The locating tool means may be left in the tubing along with a work tool, as disclosed in U.S. Pat. No. 2,673,614 to Miller, or the locating tool means may be removed from the tubing leaving a locked tool similar to the "Model `A` Locking Device" and "Model `B` Locator Tool" disclosed in a Harold Brown Company brochure entitled "Wireline Production Equipment for Flow and Pressure Control". In either event, by positioning different locator keys on the locator tool means, the running assembly is located at a different locator nipple. Problems with such systems are that the operation is performed with the locator keys engaging the locating nipple, the keys interfere with the operation of the work tool, the amount and type of manipulations that may be made to the work tool are limited, and the work tool must employ a combination of shear pins and/or large telescoping sleeves to perform the desired operation.
Occasionally, even with a wireline, due to operator inattentiveness or a malfunction of the line counter, the running assembly may overshoot the desired operating mandrel. The running assembly then must be relocated in the well before the desired operation may be performed.